SPRINGFIELD — Democratic lawmakers are moving forward with a 2015 budget based on an extension of Illinois’ temporary income tax increase.

The plan follows weeks of hearings where chiefs from state agencies overseen by Gov. Pat Quinn’s office painted doomsday scenarios about what would happen if their budgets were cut because the tax increases scheduled to end in January were allowed to expire.

Chairman Greg Harris of the House Human Services Committee, says the plan closely mirrors the $38 billion budget Quinn outlined in March that would keep tax rates in place. Quinn says letting the tax increase expire would prompt “savage cuts” in education and social programs, with an estimated revenue loss of $1.6 billion.

Unless the Legislature acts to continue the tax increase, the Illinois personal income tax rate will decline to 3.75 percent from 5 percent.

“After many hearings, we determined it was important to maintain services for families and communities,” Harris, a Chicago Democrat, said.

Republicans, who have made cutting government spending a cornerstone of their re-election campaigns, decried the move by the majority Democrats as various budget bills were being presented in the House.

“A vote for this budget is effectively a vote for the tax increase,” Rep. David McSweeney of Barrington Hills said.

The move to approve the budget is one of political expediency for Democratic leaders because passing a budget before endorsing a tax increase could serve to force the hand of several vulnerable lawmakers who are on the fence about voting for a permanent tax rise.

Senate President John Cullerton has said he has the 30 required votes for the measure’s passage in his chamber, but its fate in the House is more uncertain, where 60 votes are needed for passage.

House lawmakers are expected to hear testimony on various components the budget during committee hearings Wednesday, with a vote as early as Thursday.